Retumbo or H50BMG in 32" 300 RUM?

I just got my new full custom 300 Rum back from the gunsmith a few days ago. The barrel is a 9 twist Broughton 5C 32" finished length. I have a custom match diameter, very long throat. I am in the process of barrel break in and speed/pressure testing with Retumbo. I will start tuning for a load in the next several days. What I have discovered so far is that max load at a seating depth of 3.820" (to fit in my mag) is right at 94 grains of Retumbo. This produces 3130fps. I get the infamous Retumbo pressure spike at 95 grains. I am curious if I should steer towards H50BMG with this long barrel and throat. Does anyone have experience with this combo in extra long barrels? My gunsmith did comment that I may need H50BMG for the best velocity potential from 32". 3100fps with the 230 is very respectable but if H50BMG seems a better option I am willing to pick some up and try it. I did load two rounds up tonight with 93.5 grains of Retumbo at a seating depth of 3.950" to see what the pressure and velocity does compared to the deeper seating depth. Thanks

I've loaded for the 210's and I could only get 93 gr with the them. I'm surprised you're getting 94 gr before pressuring out with the 230's. The 230's do have a shorter bearing surface but they are also 20 gr heavier.

Anyway, I'll be testing the 230's with RL33 in my new RUM. From what I've read it looks a very good combo that should give close to 100% case capacity with good velocity. I've also read that QL list it at about the same burn rate as 50 BMG. You could try both and see what happens... it's only barrel life

Stick with Retumbo. Alternatively, consider trying H1000. Like you, I have a 32" 300RUM and have tried H50BMG and while accuracy was outstanding, velocities were very low (~2750 as I recall).

Also, your barrel is brand new. As you shoot it, you will find that it will speed up. My rifle started out shooting the 208Amax at 3150. Without changing anything about my load it has steady crept up to 3275.

Stick with Retumbo. Alternatively, consider trying H1000. Like you, I have a 32" 300RUM and have tried H50BMG and while accuracy was outstanding, velocities were very low (~2750 as I recall).

Also, your barrel is brand new. As you shoot it, you will find that it will speed up. My rifle started out shooting the 208Amax at 3150. Without changing anything about my load it has steady crept up to 3275.

Thanks Trebark! This is what I needed to hear about the H50BMG. I know that my speeds will increase as the barrel wears in, this happened with the last barrel that was on the rifle too. I have 1.5 lbs of H1000 that is "designated" to be used in the kids' 300 H&H pushing the 215 hybrids. As hard as H1000 is to come by I think I'll stick with Retumbo unless I can't pull accuracy with low ES from it.

Thanks Trebark! This is what I needed to hear about the H50BMG. I know that my speeds will increase as the barrel wears in, this happened with the last barrel that was on the rifle too. I have 1.5 lbs of H1000 that is "designated" to be used in the kids' 300 H&H pushing the 215 hybrids. As hard as H1000 is to come by I think I'll stick with Retumbo unless I can't pull accuracy with low ES from it.

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Sssshhhh...don't tell anybody but I have 8lbs of H1000 sitting on my shelf that's not being used! I tried Retumbo and H1000 in my rifle and got best performance from Retumbo so the H1000 just sits collecting dust (or another rifle build??)

How big is your kid that can shoot a 300 ouch & ouch? or does it have a brake the size of a boxcar on it?

Sssshhhh...don't tell anybody but I have 8lbs of H1000 sitting on my shelf that's not being used! I tried Retumbo and H1000 in my rifle and got best performance from Retumbo so the H1000 just sits collecting dust (or another rifle build??)

How big is your kid that can shoot a 300 ouch & ouch? or does it have a brake the size of a boxcar on it?

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My boys are 11 and 12 right now. They were actually shooting my braked RUM at 8 and 9 years old out to 950 yards and did surprisingly well even then. They would keep on burning powder if I kept giving them shells! And yes, the H&H has a break on it. In fact I just let them shoot it today at 800 yards and they did their part. Dad just needed to be a little better on giving them their wind holds in a shifting wind Feel blessed that you have 8lbs of H1000!!!

I'd be thinking of rl33 in your 30 rum. I'm working with it in my 30 rum bdl lh and she's consistantly sub moa with the 225 hornady hpbt and usually 1/2 moa. Good case fill too. Rl50 was a bit harsh on case fill when I tried it last year.

I'd be thinking of rl33 in your 30 rum. I'm working with it in my 30 rum bdl lh and she's consistantly sub moa with the 225 hornady hpbt and usually 1/2 moa. Good case fill too. Rl50 was a bit harsh on case fill when I tried it last year.

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I actually considered buying some several months ago to try for this project. However, no one has been able to convince me that RL33 is any less temp sensitive then other Alliant powders. I have asked that question on this forum before. RL22 is particularly bad. I had a really bad experience with 22 several years ago and switched to Hodgdon Extreme powders in everything I load for. If someone wants to do a temperature test on a hot summer day with hot ammo verses ice bagged ammo and shows that there is very little velocity difference I might consider it. I just have not been able to find that information yet.

I actually considered buying some several months ago to try for this project. However, no one has been able to convince me that RL33 is any less temp sensitive then other Alliant powders. I have asked that question on this forum before. RL22 is particularly bad. I had a really bad experience with 22 several years ago and switched to Hodgdon Extreme powders in everything I load for. If someone wants to do a temperature test on a hot summer day with hot ammo verses ice bagged ammo and shows that there is very little velocity difference I might consider it. I just have not been able to find that information yet.

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I also prefer the Hodgdon powders but they are not completely insensitive to temp changes. I have seen 100 fps shift in velocity from one lot to another of Retumbo and heard similar of H1000. Not sure about RL33 but I suspect it's more temp sensitive than the Extreme powders but maybe less than the other Alliant powders.

Bottom line for me is, no matter what powder you use you will have to make adjustments for temp swings. The question is how much. My 300 RUM will primarily be a hunting rifle and used in the Fall for general big game and the Spring for Spring Bear when temps will be mostly cool to cold.

The advantage to RL33 is it will fill your case better than Retumbo which will fill your case batter than H1000. And it will likey give you better velocities.

rl17, ar comp, rl33, and rl50 are not swedish powders like the other rl series, they are swiss. I haven't had any more/ less trouble with rl powders in temp. swings than any other powder. You can't take the variations out of the barrel, primer, case, bullet, air density, and your shoulder (cold weather = more clothes and less resistance to recoil, hence less velocity) so I'm not so sure bothering to use a brand just because it is slightly more temp stable is worth my time.
I've loaded rl7, 15, 17, 19, 22, 25, 33, and 50 in the last year. My total Hodgdon choices are h4895 (which I'll replace with I 4895 when the h is out), h4350, superformance, and retumbo.

rl17, ar comp, rl33, and rl50 are not swedish powders like the other rl series, they are swiss. I haven't had any more/ less trouble with rl powders in temp. swings than any other powder. You can't take the variations out of the barrel, primer, case, bullet, air density, and your shoulder (cold weather = more clothes and less resistance to recoil, hence less velocity) so I'm not so sure bothering to use a brand just because it is slightly more temp stable is worth my time.
I've loaded rl7, 15, 17, 19, 22, 25, 33, and 50 in the last year. My total Hodgdon choices are h4895 (which I'll replace with I 4895 when the h is out), h4350, superformance, and retumbo.

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I'm sure RL33 is a great powder and I've heard good things about it's velocity potential. While there are a lot of variables I can't control very well as you mentioned, I choose to go with the least temp sensitive powder so that it's one less thing to cause a problem or have to account for. If down the road someone does some thorough, hard testing of the temperature sensitivity of RL33 and it proves to be comparable to Hodgdon Extreme powders, then you bet I'll try it. In fact I hope it does turn out to be temp insensitive because of the good things I've been hearing about velocity improvements over other powders.

Nothing wrong using 94gr Retumbo with good accuracy and velocity spreads if this is the case. I'll take Retumbo over a "slower burning faster bullet powder" anyday if my velocity spreads increase. I use Retumbo in my 300 Rum with the 230's and have great results. You may not gain an overall advantage changing to H50. However, if Retumbo isn't working by all means try a different powder.

Nothing wrong using 94gr Retumbo with good accuracy and velocity spreads if this is the case. I'll take Retumbo over a "slower burning faster bullet powder" anyday if my velocity spreads increase. I use Retumbo in my 300 Rum with the 230's and have great results. You may not gain an overall advantage changing to H50. However, if Retumbo isn't working by all means try a different powder.

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Velocity spreads right now are my main concern. I have not had time to dive into serious load development yet. I just know where pressure starts. If it likes 93-93.5 grains of Retumbo then I'll be running somewhere around 3065-3100fps. As the barrel wears in I'm sure this will increase as someone previously posted. My goal is low ES and no more than .25MOA vertical spread. I should be able to get this weapon to shoot sub .5MOA. I'll keep posting updates as development continues.

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